System and Method for Selecting Operating Parameters in a Communications System

ABSTRACT

A method for configuring a first base station within a cluster in a communications system having a plurality of cluster includes optimizing an operating parameter of the first base station in accordance with first utility function results from a first utility function associated with the first base station and second utility function results from a second utility function associated with a second base station within the cluster, the first utility function results and the second utility function results according to multiple settings for the operating parameter of the first base station, a first initialized setting of the operating parameter for the second base station, and a second initialized setting of the operating parameter for an external base station outside the cluster. The method also includes sharing the optimized operating parameter with the external base station.

TECHNICAL FIELD

The present invention relates generally to digital communications, andmore particularly to a system and method for selecting operatingparameters in a communications system.

BACKGROUND

In many second generation (2G) and third generation (3G) communicationssystems, a base station (also commonly referred to as a controller, acommunications controller, a NodeB, an evolved NodeB, and the like)makes its own decision on how to select users (also commonly referred toas mobile stations, subscribers, terminals, user equipment, and thelike) for transmission. Additionally, operating parameters, such astransmit power level, data rate, and the like, may be left unchanged foran extended period of time.

In an attempt to improve network capacity, multiple-inputmultiple-output (MIMO) techniques have been developed, wherein basestations and/or mobile stations are equipped with multiple antennas (forexample, multiple transmit antennas, multiple receive antennas, or bothmultiple transmit antennas and multiple receive antennas). A commonlyused MIMO technique involves the precoding of a transmission to shapethe transmission towards its intended recipient. The precoding can alsobe applied to a MIMO receiver. The precoding information used in a MIMOcommunications system is also a operating parameter.

Another technique used to improve network capacity is coordinatedmultipoint processing (CoMP). In general, CoMP schemes employ multipletransmitters and/or receivers to jointly optimize transmissionparameters. In a communications system utilizing CoMP, the CoMPconfiguration is another operating parameter.

SUMMARY OF THE INVENTION

Example embodiments of the present invention which provide a system andmethod for selecting operating parameters in a communications system.

In accordance with an example embodiment of the present invention, amethod for configuring a first base station within a cluster in acommunications system having a plurality of cluster is provided. Themethod includes optimizing an operating parameter of the first basestation in accordance with first utility function results from a firstutility function associated with the first base station and secondutility function results from a second utility function associated witha second base station within the cluster, the first utility functionresults and the second utility function results according to multiplesettings for the operating parameter of the first base station, a firstinitialized setting of the operating parameter for the second basestation, and a second initialized setting of the operating parameter foran external base station outside the cluster. The method also includessharing the optimized operating parameter with the external basestation.

In accordance with another example embodiment of the present invention,a method for configuring a first internal base station within a clusterin a communications system having a plurality of clusters is provided.The method includes using a first utility function to generate a firstresult according to a first parameter setting of an operating parameterof the first internal base station within the cluster, an internalinitialized parameter setting of the operating parameter of a secondinternal base station within the cluster, and an external initializedparameter setting of the operating parameter of an external base stationoutside the cluster. The method also includes using the first utilityfunction to generate a second result according to a second parametersetting of the operating parameter of the first internal base stationwithin the cluster, the internal initialized parameter setting of theoperating parameter of the second internal base station, and theexternal initialized parameter setting of the operating parameter of theexternal base station. The method additionally includes receiving athird result from the second internal base station, the third resultgenerated by a second utility function using the first parameter settingof the first internal base station, the internal initialized parametersetting of the second internal base station, and the externalinitialized parameter setting of the external base station. The methodfurther includes receiving a fourth result from the second internal basestation, the fourth result generated by the second utility functionusing the second parameter setting of the internal base station, theinternal initialized parameter setting of the second internal basestation, and the external initialized parameter setting of the externalbase station. The method also includes selecting one of the first andsecond parameter settings of the internal base station according to acomparison of a summation of the first result and the third result witha summation of the second result and the fourth result, therebyproducing a first selected one, and using the first selected one as anew initialized parameter setting for the internal base station.

In accordance with another example embodiment of the present invention,a first base station is provided. The first base station includes aprocessor, and a transmitter operatively coupled to the processor. Theprocessor optimizes an operating parameter of the first base station inaccordance with first utility function results from a first utilityfunction associated with the first base station and second utilityfunction results from a second utility function associated with a secondbase station within a cluster, the first utility function results andthe second utility function results according to multiple settings forthe operating parameter of the first base station, a first initializedsetting of the operating parameter for the second base station, and asecond initialized setting of the operating parameter for an externalbase station outside the cluster. The transmitter shares the optimizedoperating parameter with the external base station.

One advantage of an embodiment is that the complexity in determiningoperating parameter settings of base stations in a communications systemis reduced by partitioning the communications system into a plurality ofclusters. Therefore, the determining of the operating parameter settingsmay be accomplished without requiring the availability of a large amountof computational resources.

A further advantage of an embodiment is that both a centralizedtechnique and a partially distributed technique for determining theoperating parameter settings of base stations are presented. Therefore,significant implementation flexibility is available.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawing, in which:

FIG. 1 a illustrates an example communications system according toexample embodiments described herein;

FIG. 1 b illustrates an example diagram of transmit power of two basestations according to example embodiments described herein;

FIG. 2 a illustrates an example communications system with a centralcontroller, wherein communications system is partitioned into aplurality of non-overlapping clusters according to example embodimentsdescribed herein;

FIG. 2 b illustrates an example communications system, whereincommunications system is partitioned into a plurality of non-overlappingclusters according to example embodiments described herein;

FIG. 3 a illustrates an example flow diagram of operations in selectingoperating parameter settings of base stations in a cluster of acommunications system according to example embodiments described herein;

FIG. 3 b illustrates an example flow diagram of operations in optimizingoperating parameter settings of base stations in a cluster according toexample embodiments described herein;

FIG. 4 a illustrates an example flow diagram of operations occurring ina cluster controller as it participates in determining operatingparameter settings according to example embodiments described herein;

FIG. 4 b illustrates an example flow diagram of operations occurring ina base station as it schedules transmissions for its UEs according toexample embodiments described herein;

FIG. 5 a illustrates an example flow diagram of operations occurring ina cluster controller as it participates in a distributed version ofoperating parameter setting selection according to example embodimentsdescribed herein;

FIG. 5 b illustrates an example flow diagram of operations occurring ina base station as it participates in a distributed version of operatingparameter setting selection, wherein the base station is selecting itsoperating parameter settings according to example embodiments describedherein;

FIG. 5 c illustrates an example flow diagram of operations occurring ina base station as it participates in a distributed version of operatingparameter selection, wherein the base station is assisting another basestation select its operating parameter settings according to exampleembodiments described herein;

FIG. 6 illustrates an example flow diagram of operations occurring in acluster controller as it participates in a centralized version ofoperating parameter selection according to example embodiments describedherein;

FIG. 7 a illustrates an example first communications device according toexample embodiments described herein;

FIG. 7 b illustrates a detailed view of an example parameter selectingunit that operates in a distributed manner according to exampleembodiments described herein;

FIG. 7 c illustrates a detailed view of an example parameter selectingunit that operates in a centralized manner according to exampleembodiments described herein;

FIG. 8 illustrates an example first communications device according toexample embodiments described herein.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The operating of the current example embodiments and the structurethereof are discussed in detail below. It should be appreciated,however, that the present invention provides many applicable inventiveconcepts that can be embodied in a wide variety of specific contexts.The specific embodiments discussed are merely illustrative of specificstructures of the invention and ways to operate the invention, and donot limit the scope of the invention.

One embodiment of the invention relates to determining operatingparameter settings for base stations of a communications system that ispartitioned into a plurality of clusters. For example, a clustercontroller selects or coordinates the selection of settings foroperating parameters of base stations in its cluster as part of anoptimization process according to initialized or previous settings ofoperating parameters of base stations in the cluster as well asinitialized or previous settings of operating parameters of basestations in other clusters. The selected settings operating parametersof base stations in the cluster are shared with other clusters, whichmay lead to additional selections of settings of the operatingparameters. For example, a base station upon receiving its selectedsettings of the operating parameters may estimate conditions for itsserved user equipments and then schedules its user equipments and setstheir data rates based on the estimated conditions.

The present invention will be described with respect to exampleembodiments in a specific context, namely a Third Generation PartnershipProject (3GPP) Long Term Evolution (LTE) compliant communications systemsupporting MIMO and/or CoMP operation. The invention may also beapplied, however, to other standards compliant communications systems,such as those that are compliant to IEEE 802.16, WiMAX, and the like, aswell as non-standards compliant communications systems.

FIG. 1 a illustrates a communications system 100. Communications system100 includes a plurality of base stations which may or may not havedifferent transmit power capabilities. As an example, some base stationsmay be classified as full transmit power base stations such as a macrobase stations (macro BS) including macro BS 105, macro BS 107, and macroBS 109. While other base stations may be classified as low power basestations, such as pico base stations (pico BS) including pico BS 110,pico BS 112, and pico BS 114. Another example of a low power basestation is a femto cell.

Communications system 100 also includes a plurality of user equipment(UE), such as UE 120 and UE 122. As shown in FIG. 1 a, macro BS 105 istransmitting to UE 120 and pico BS 110 is transmitting to UE 122.However, transmissions from macro BS 105 may also impact UE 122, whiletransmissions from pico BS 110 may also impact UE 120. Furthermore,transmissions from macro BS 109 may also impact UE 120.

The base stations of communications system 100 may be partitioned into aplurality of non-overlapping clusters. In general, a cluster may includeone or more base stations, and due to the non-overlapping property, asingle base station belongs to only one cluster. A cluster with multiplebase stations may be referred to as a CoMP set. The base stations in acluster may have the same or different identification numbers. As shownin FIG. 1 a, a first cluster 130 includes macro BS 105 and pico BS 110,a second cluster 132 includes macro BS 107, pico BS 112, and pico BS114, and a third cluster 134 includes macro BS 109. It is noted thatFIG. 1 illustrates an illustrative example of a plurality ofnon-overlapping clusters for communications system 100 and that otherconfigurations of non-overlapping clusters are possible forcommunications system 100.

FIG. 1 b illustrates a diagram 150 of transmit power of two basestations. Diagram 150 depicts an almost blank subframe (ABS) techniquefor 10 time slots. In time slots 1, 4, and 7, base station 1 transmitsABS subframes. Therefore, in these subframes, there is no or very littleinterference from base station 1 to the UEs of base station 2,therefore, base station 2 may transmit to its UEs at higher data rates.

Although the discussion focuses on a communications system beingpartitioned into a plurality of non-overlapping clusters, the exampleembodiments presented herein may be operable with overlapping clusters,as well as a combination of non-overlapping and overlapping clusters.Therefore, the discussion of non-overlapping clusters should not beconstrued as being limiting to either the scope or the spirit of theexample embodiments.

FIG. 2 a illustrates a communications system 200 with a centralcontroller, wherein communications system 200 is partitioned into aplurality of non-overlapping clusters. Communications system 200includes clusters 205, 207, 209, and 211. According to a first exampleembodiment, each cluster includes a cluster controller that isresponsible for determining operating parameter settings for basestations within its cluster. Furthermore, a cluster controller may alsocoordinate with other cluster controllers and/or a central controller toshare operating parameter settings. As an example, cluster 205 includescluster controller 215 coupled to macro BS 220, macro BS 222, pico BS224, and pico BS 226, while cluster 207 includes cluster controller 230coupled to macro BS 232. According to a second example embodiment, basestations in a subset of base stations in a communications system isresponsible for determining operating parameter settings for themselves.

Communications system 200 also includes a central controller 235.Central controller 235 may be coupled to the cluster controllers of theplurality of non-overlapping clusters in communications system 200.Central controller 235 may be responsible for coordinating the operationof the cluster controllers, coordinating the sharing of operatingparameter settings from the cluster controllers, determining when thecluster controllers initiate the determining the operating parametersettings, determining when the cluster controllers stop the determiningof the operating parameter settings, and the like. It is noted that acommunications system may have multiple central controllers, especiallyif it there is a large number of clusters. The multiple centralcontrollers may be coupled to each other, they may be arranged in ahierarchical manner, or they may be disjoint.

According to the first example embodiment, the cluster controllers maybe coupled to the base stations over a high speed interface, such as anX2 interface. Similarly, the cluster controllers may be coupled tocentral controller 235 over a high speed interface, such as an X2interface. However, the coupling of the cluster controllers, the basestations, and the central controller over a high speed interface mayalso apply to other example embodiments discussed herein.

FIG. 2 a illustrates a communications system 250, wherein communicationssystem 250 is partitioned into a plurality of non-overlapping clusters.Communications system 250 includes clusters 255, 257, 259, and 261.However, the cluster controllers in communications system 250 aredirectly coupled to one another (e.g., with a high speed interface, suchas an X2 interface) rather than to a central controller. The clustercontrollers themselves may be responsible for coordinating the operationof the cluster controllers, coordinating the sharing of operatingparameter settings from the cluster controllers, determining when thecluster controllers initiate the determining of the operating parametersettings, determining when the cluster controllers stop the determiningof the operating parameter settings, and the like.

As an example, in a downlink of an orthogonal frequency divisionmultiplexed (OFDM) based communications system, such as 3GPP LTE or 3GPPLTE-A, data to be transmitted to a UE is sent on resource block(s) (RB),with each RB comprising several subcarriers and several OFDM symbols.Operating parameters of a RB include transmit power level p andprecoding matrix U. According to an example embodiment, a transmit powerlevel p_(i) of an i-th base station may be selected from a discrete setof K transmit power levels expressible as

pε{p₁,p₂, . . . , p_(K)}.  (1)

However, in general, the transmit power level may be taken from anon-discrete set of possible values. While the precoding matrix U may beadaptively designed to match channel characteristics. The precodingmatrix U may also be selected from a set of M possible precodingmatrices expressible as

Uε{U₁,U₂, . . . , U_(M)}.  (2)

It may be beneficial to express U_(i) as null directions rather thanprecoded directions (i.e. vectors V_(i) for which the transmittedprecoder U_(i) are orthogonal, i.e., <U_(i), V_(i)>≦ε).

According to the first example embodiment, it may be possible to selectsettings for operating parameters, such as transmit power level,precoder, modulation and coding scheme of transmissions, location ofreference signals (e.g., channel state information reference signals),pilot signal boosting level, frequency selective scheduling or frequencydiversity scheduling, handover parameter (e.g., range extension, utilityvalues, and the like), antenna tilt, antenna pattern, transmission rank,and the like, according to a utility function F(p_(k),U_(m)). However,the selecting of settings for the operating parameters according to autility function may also apply to other example embodiments discussedherein. The utility function may be a mathematical expression of arelationship between the operating parameters and may used to assignsettings to the operating parameters. As an example, a utility functionmay provide an indication of quantitative measure, such as aninstantaneous data rate r_(i) of an i-th UE, or function of the datarate, such as

${\log\left( \frac{r_{i}}{r_{avg}} \right)},$

where r_(avg) is an average data rate of the i-th UE, according to arelationship between the operating parameters. A result of the utilityfunction may be the result of an application of specific operatingparameter settings to the utility function. The utility function may bedesigned so that a set of operating parameters settings may maximize theutility function for a RB group (RBG).

As an example, the selection of a specific operating parameter settingfrom possible settings of the operating parameter using a utilityfunction and its utility function result, such as instantaneous datarate or a function of instantaneous data rate may be as follows: When aUE sends feedback information, e.g., channel state information (CSI) atan n-th transmission time interval (TTI), or in general, channel qualityindicator (CQI), the base stations determine an interference at the n-thTTI, I_(TTI=n), where the interference may be determined according tolong term pathloss information (measured by reference signal receivedpower (RSRP) in the downlink or sounding reference signal (SRS) in theuplink, for example). The interference at the n-th TTI is expressible as

${I_{{TTI} = n} = {\sum\limits_{i = 1}^{L}{P_{i,{{TTI} = n}} \times \beta_{i}}}},$

where β_(i) is the pathloss between a UE and neighboring base stationBSi, L is the number of neighboring base stations, and P_(i,TTI=n) isthe operating parameter setting (e.g., transmit power level) of BSi atthe n-th TTI. It is noted that the use of averaging for interference isnot precluded in which P_(i,TTI=n) is replaced by a function of theprevious operating parameters. As an example, the function may be asliding window over the TTI for which the UE is to perform interferencemeasurements.

When determining the instantaneous data rate of the UE at a (n+k)-thTTI, the base station may recalculate the interference at the (n+k)-thTTI, which is expressible as

$I_{{TTI} = {n + k}} = {\sum\limits_{i = 1}^{L}{P_{i,{{TTI} = {n + k}}} \times {\beta_{i}.}}}$

Then, from the feedback information, e.g., CQI, which may be in the formof the MCS level, the base station may convert the MCS level into a SINRvalue at the n-th TTI, SINR_(TTI=n), to account for short term fading.Typically, the conversion of MCS level to SINR value may be performedusing a lookup table. An adjusted SINR at the (n+k)-th TTI may then bedetermined as

${SINR}_{{TTI} = {n + k}} = {{SINR}_{{TTI} = n} \times {\frac{I_{{TTI} = n}}{I_{{TTI} = {n + k}}}.}}$

From the adjusted SINR, the MCS level may be chosen for the UE. Onceagain, the conversion from the adjusted SINR to the MCS level may beimplemented using a lookup table, which may be the same or differentfrom the lookup table used to convert MCS level to SINR value. The MCSlevel, which by definition specifies a code rate, specifies aninstantaneous data rate for the UE. If desired, a function may beapplied to the instantaneous data rate. As an example,

${\log\left( \frac{r_{i}}{r_{avg}} \right)},$

where r_(avg) is an average data rate of the i-th UE and r_(i) is theinstantaneous data rate of the i-th UE. The instantaneous data rate orthe function of the instantaneous data rate, i.e., the utility functionresult may be used to select the setting of the operating parameter.

In order to obtain the utility function values for the base station, theutility function values for the various UEs may be selected, e.g., usingmaximization function. However, other quality of service factors, suchas a delay constraint, a retransmission priority, and the like, may beconsidered.

According to the first example embodiment, there may be a number of waysto select the settings of the operating parameters for the base stationsin a cluster. One way to select the settings of the operating parametersis to sequentially select the operating parameter settings for each ofthe base stations according to an ordering, which may be specific orrandom, as part of an optimization process. The sequential selection ofthe operating parameter settings as part of an optimization process aredescribed herein. Another way to select the operating parameter settingsis to perform an exhaustive search for the base stations in the cluster.Another way to select the operating parameter settings is to perform anexhaustive search within a locality in combination with a sequentialordering of localities. However, the selecting of settings for theoperating parameters for base stations in a cluster may also apply toother example embodiments discussed herein.

According to the first example embodiment, the selection of the settingsof the operating parameters may be a multi-step process. A first stepmay involve joint optimization within a cluster, with an entity within acluster optimizing operating parameters of base stations within thecluster assuming initialized settings for base stations outside of thecluster. A second step may involve inter-cluster information sharing.After joint optimization to select settings for the operatingparameters, the information may be shared with other clusters, throughbroadcasting, for example. The clusters may make use of the informationto perform additional optimization or not.

FIG. 3 a illustrates a flow diagram of operations 300 in selectingoperating parameter settings of base stations in a cluster of acommunications system. Operations 300 may be indicative of operationsoccurring in a cluster controller, such as cluster controller 215 andcluster controller 230, as the cluster controller participates indetermining operating parameter settings for base stations of acommunications system.

Operations 300 may begin with an initialization of operating parametersettings for the base stations of the cluster (block 305). According tothe first example embodiment, the operating parameters may be set todefault settings of the operating parameters upon a first time that theselecting of the settings of the operating parameters is performed,wherein the default settings may be specified by an operator of thecommunications system, a technical standard to which the communicationssystem adheres, and the like. The initialized operating parametersettings may be used in subsequent settings until actual settings of theoperating parameters are selected. However, the setting of the operatingparameter to default settings may also apply to other exampleembodiments discussed herein.

The cluster controller may optimize the operating parameter settings ofthe base stations in the cluster using the initialized operatingparameter settings for the base stations in the cluster as well as theinitialized operating parameter settings for base stations outside ofthe cluster (block 307). According to the first example embodiment, thecluster controller may optimize the operating parameter settings for thebase stations in a sequential order according to a selected processingorder, and when optimizing the operating parameter settings for an i-thbase station, the cluster controller may determine utility functionresults for each possible operating parameter setting of the i-th basestation according to: each possible operating parameter setting of thei-th bases station, initialized operating parameter settings for eachbase station in the cluster, and initialized operating parametersettings for base stations outside of the cluster. However, the clustercontroller optimizing the operating parameter settings in a sequentialorder may also apply to other example embodiments discussed herein. Adetailed discussion of the optimization of the operating parametersettings is provided below.

The cluster controller may share the operating parameter setting for thebase stations in the cluster with base stations in other clusters (block309). The cluster controller may directly share the operating parametersettings with other cluster controllers or it may share the operatingparameter settings with a centralized controller.

The cluster controller may perform a check to determine if it shouldcontinue selecting operating parameter settings of the base stations inthe cluster (block 311). As an example, the cluster controller maycontinue selecting operating parameter settings of the base stations inthe cluster or of some of the base stations in the cluster if thecluster controller has sufficient computational resources and/or timethat it can dedicate to the selection. If the cluster controller doesnot have sufficient computation resources and/or time to selectoperating parameter settings for all of its base stations, then thecluster controller may select operating parameter settings for a subsetof its base stations.

The cluster controller may send the operating parameter settings to thebase stations in the cluster (block 313), which may use the operatingparameter settings to estimate a metric for the UEs that they areserving (block 315). The base stations may utilize the metrics for theUEs to schedule the UEs, as well as adjust the data rates of the UEs(block 317). A detailed description of the operations of the basestations is provided below.

FIG. 3 b illustrates a flow diagram of operations 350 in optimizingoperating parameter settings of base stations in a cluster. Operations350 may be indicative of operations occurring in a base station (adistributed algorithm) or a cluster controller (a centralized algorithm)as the base station or the cluster controller selects operatingparameter settings as part of an optimization operation.

Operations 350 may begin with each base station obtaining initializedoperating parameter settings of other base stations in the cluster(block 355). Each base station may receive the initialized operatingparameter settings from the cluster controller or directly from theother base stations.

For an i-th base station (block 357), as determined according to aselected processing order specified by the cluster controller, forexample, utility function results of the i-th base station may bedetermined according to possible operating parameter settings for thei-th base station, initialized operating parameter settings for theother base stations in the cluster, and initialized operating parametersettings for base stations outside of the cluster (block 359).

The selection of the operating parameter settings may be performed byselecting operating parameter settings that optimizes a summation ofutility function results for the actual operating parameter settings ofthe i-th base station (block 361). As an example, an operating parametersetting that maximizes (or minimizes) the summation of utility functionresults corresponding to the operating parameter setting may be selectedas the optimal operating parameter setting. It is noted that maximizingthe summation or minimizing the summation may be examples of optimizingcriterion.

The selected operating parameter settings may then be shared with otherbase stations in the cluster (block 363) and if there are more basestations in the cluster with operating parameter settings that have notbeen selected (block 365), operations 350 may return to block 357 toselect another i-th base station. If the operating parameter settingshave been selected for all of the base stations in the cluster, theselected operating parameter settings may be stored for subsequent use(block 367).

Since the operating parameters of each base station may change everytransmission time slot to maximize communications system performance,each base station may be able to adaptively select data rates for itsUE. Therefore, the transmit power information of surrounding basestations as well as pathloss from the UE to neighboring base stationsmay be exploited. The transmit power information may be shared among thebase stations, while the pathloss can be derived from information, suchas reference signal received power reports of neighboring base stationsas reported by the UEs, uplink received signals at neighboring basestations, distance from base stations to UE, or a combination thereof.

In general, in a communications system, the UE may report its possibledata rate by using channel quality indicator (CQI). When the UE reportsits CQI, the base stations may record an interference amount I_(i) fromother base stations to the UE, based on instantaneous transmit power ofneighboring base stations and the pathloss of the UE. When the basestation calculates possible data rate of UEs for scheduling purposes, aninterference amount I2 from other base stations is calculated again,according to current knowledge of the transmit power as well asbeamforming of neighboring base stations. A difference of theinterference Δ=I₂−I₁ may be used to adjust the actual data rates of theUEs. As an example, the data rate may be increased proportionally ifΔ_(I)>0, and vice versa.

Typically, if the interference at the time of transmission is differentfrom the interference at the time of the CQI report from the UE, thetransmission rank may be adjusted accordingly. As an example, if theinterference has decreased, then the transmission rank may be increasedto obtain a greater data rate.

The selection of the settings of the operating parameters may be appliedin any combination of RBGs in a single TTI. As an example, there may beapplied on a per RBG basis or a per TTI basis. Application of anoperating parameter setting on a per RBG basis means that the operatingparameter of a single RBG may be optimized independently from otherRBGs. As an example, considering a situation wherein transmit power isthe operating parameter, then the transmit power setting per TTI mayimpose another constraint, namely the utility of all RBGs, expressibleas

${\sum\limits_{i = 0}^{{num}_{BS}}{\sum\limits_{k = 1}^{{num}_{RBG}}{U_{i}\left( {P_{j},{RBG}_{k}} \right)}}},$

in one TTI is maximized. The transmit power setting per TTI means thatthe power levels over all RBGs within one TTI is the same. Therefore,the performance of per TTI applications may be worse than per RBGapplications.

FIG. 4 a illustrates a flow diagram of operations 400 occurring in acluster controller as it participates in determining operating parametersettings as part of an optimization process. Operations 400 may beindicative of operations occurring in a cluster controller, such ascluster controller 215 and cluster controller 230, as the clustercontroller participates in determining operating parameter settings forbase stations of a communications system.

The communications system may be partitioned in a plurality ofnon-overlapping clusters of base stations, which means that each basestation in the communications system belongs to a single cluster. Fordiscussion purposes, let F_(i) (p_(i,k),U_(i,m)) be the utility functionfor the i-th base station, where i={1, 2, . . . , N} and N is the numberof base stations in a non-overlapping cluster for a RBG. According tothe first example embodiment, the utility functions are formulated sothat the settings of the operating parameters may be determined bymaximizing a summation of all utility functions of base stations withina single cluster. Alternatively, the utility functions are formulated sothat the settings of the operating parameters may be determined byminimizing a summation of all utility functions of base stations withina single cluster. It is noted that maximizing the summation orminimizing the summation may be examples of optimizing criterion.However, the formulation of the utility functions may also apply toother example embodiments discussed herein.

Operations 400 may begin with the cluster controller initializing theoperating parameters of base stations in the cluster to initial settings(block 405). As discussed previously, operating parameters may includetransmit power level, precoder, modulation and coding scheme oftransmissions, location of reference signals (e.g., channel stateinformation reference signals), pilot signal boosting level, frequencyselective scheduling or frequency diversity scheduling, handoverparameter (e.g., range extension, utility values, and the like), antennatilt, antenna pattern, transmission rank, and the like. As an example,if the operating parameter is the transmit power level, then the initialsetting of the operating parameter may be full transmit power or afraction of full transmit power, such as half, quarter, and the like.According to the first example embodiment, on an initial determining ofoperating parameter settings for a first transmission period for thebase stations, the cluster controller initializes the operatingparameters of the base stations to initial settings that may beprespecified by an operator of the communications system, a technicalstandard to which the communications system follows, historicalinformation regarding the operating parameters, and the like. Although,the cluster controller initializing the operating parameters of the basestations to initial settings that may be prespecified by an operator ofthe communications system, a technical standard to which thecommunications system follows, historical information regarding theoperating parameters, and the like, may also apply to other exampleembodiments discussed herein. However, on subsequent determinations ofthe operating parameter settings, the cluster controller may utilizeoperating parameters settings determined for an earlier transmissionperiod, such as a transmission period immediately preceding a currenttransmission period, an averaging (or some other function, such asweighted average, weighted sum, and the like) of the operating parametersettings determined for the earlier transmission period(s), and thelike.

The cluster control may select the operating parameter settings of thebase stations in the cluster (block 410). As an example, the selectionof the operating parameter settings for base stations occurs on aresource block group (RBG) basis and once the operating parametersettings are selected for a particular RBG, unused portions of someoperating parameters, such as transmit power level, may be used by otherbase stations with RBGs that utilize all of the corresponding operatingparameters to obtain additional performance improvement. As an example,if the operating parameter is transmit power level and in one RBG for aparticular base station, the selected transmit power level is not a fulltransmit power level, then other base stations with the selectedtransmit power level at the full transmit power level may exploit theunused transmit power level in the one RBG to obtain additionalperformance gain. As another example, if one RBG uses only a fraction offull transmit power level, the unused energy of the one RBG may be usedfor other RBG(s) to further boost performance, for example, of cell edgeUEs, given a constraint on the total transmit power, which may be on aper transmit antenna basis or a per base station transmit antenna poolbasis.

According to the first example embodiment, the selection of theoperating parameter settings of the base stations may be according topossible settings of the operating parameters of the base stations, theinitialized settings of the operating parameters of the base stations inthe cluster, and initialized settings of the operating parameters of thebase stations that are not in the cluster. The use of the initializedsettings of the operating parameters of the base stations that are notin the cluster helps to simplify the selection of the operatingparameter settings of base stations in the cluster by significantlyreducing a computational space of computations that are made. Thereduced computational space of computations helps to reduce thecomputational load on a network entity (such as the cluster controller,a base station, a dedicated entity in the communications system thatperforms the computations used in selecting the operating parametersettings of the base stations, and the like) performing the selection,and hence the optimization. However, the selection of the operatingparameter settings of the base stations may be according to possiblesettings of the operating parameters of the base stations, theinitialized settings of the operating parameters of the base stations inthe cluster, and initialized settings of the operating parameters of thebase stations that are not in the clustermay also apply to other exampleembodiments discussed herein.

Additionally, the partitioning of the communications system into theplurality of non-overlapping clusters further helps to reduce thecomputational space of computations by reducing a number of basestations in a single cluster. A trade-off may be made in a number ofbase stations in a cluster and a number of clusters in the plurality ofnon-overlapping clusters versus a number of cluster controllers andcomputational complexity involved in selecting the operating parametersettings of base stations in the clusters. Generally, if there arerelatively few clusters, then the number of cluster controllers issmaller, thereby reducing implementation costs. However, with fewerclusters, each cluster may have more base stations, hence, individualcluster controllers, base stations, dedicated entities, and the like,may have greater computational load. Conversely, if there are manyclusters, then the implementation costs may be greater due to the largernumber of cluster controllers, however, individual cluster controllers,base stations, dedicated entities, and the like, may have lessercomputational load. It is noted that with appropriate signaling, acluster controller may be a base station within a respective cluster, inwhich the base station will decide upon its operating parameter settingswhile neglecting the selections of the operating parameter settings madein the other cells and/or base stations within it's cluster (i.e.,assuming that the selections of the operating parameter settings madeare the default and/or previously selected selections).

According to the first example embodiment, the selection of theoperating parameter settings for the base stations in the cluster may bemade according to a selected processing order for the base stations inthe cluster. The selected processing order may, in general, specify asequential processing order for the base stations in the cluster. Sincethe optimization problem may be a non-convex problem, the selectedprocessing order may make an impact on the performance. One way to helpalleviate the problem is to have several iterations of optimization withdifferent selected processing orders. As an example, if there are fourbase stations in a cluster, then an example selected processing ordermay be base station 1, base station 3, base station 4, and base station2. The selected processing order may be selected by the clustercontroller, predetermined by an operator of the communications system,specified in a technical standard, and the like. As an example, theselected processing order may be made according to factors such as basestation type, distance from cluster controller, bandwidth of aconnection with the cluster controller, a number of UE supported by thebase stations, priority of UE supported by the base stations, and thelike. However, the selection of the operating parameter settingsaccording to the selected processing order may also apply to otherexample embodiments discussed herein.

For a first base station in the selected processing order, the settingsof the operating parameters may be selected using initialized settingsfor the operating parameters of other base stations in the cluster andinitialized settings for base stations that are not in the cluster. Oncethe settings of the operating parameters for the first base station isselected, the selected operating parameter settings for the first basestation may then be used in the selection of operating parametersettings for remaining base stations in the cluster, replacing theinitialized settings of the operating parameters of the first basestation. The selection of the operating parameter settings for the basestations in the cluster may continue until the operating parametersettings of the remaining base stations in the cluster have beenselected, thereby completing the optimization process. A detaileddescription of the selection of the operating parameter settings isprovided below. According to the first example embodiment, to reducecomplexity and to allow different base stations to perform theiroperations in parallel, the operating parameter settings of the firstbase station may not be passed to other base stations before theythemselves have selected their own operating parameter settings.However, the operating parameter settings of the first base station notbeing passed to other base stations before they themselves have selectedtheir own operating parameter settings may also apply to other exampleembodiments discussed herein.

According to the first example embodiment, the selected processing orderfor a cluster may remain the same each time that the operating parametersettings for the base stations in the cluster are selected.Alternatively, the selected processing order for a cluster may bechanged each time that the operating parameter settings for the basestations in the cluster are selected. Alternatively, the selectedprocessing order for a cluster is selected at random. Alternatively, theselected processing order of a cluster is selected at random each timethat the operating parameter settings for the base stations in thecluster are selected. However, the selected processing order changing orremaining the same that the operating parameter settings are selectedmay also apply to other example embodiments discussed herein.

According to the first example embodiment, when selecting operatingparameter settings, it may be possible that the selected operatingparameter settings be different from earlier operating parametersettings. Therefore, it may be possible to add an additional constraintthat imposes a penalty (e.g., a reduction in a utility function result)if the selected operating parameter settings are different from theearlier operating parameter settings. Additionally, the penalty may bescaled depending on the difference between the selected operatingparameter settings and the earlier operating parameter settings.However, the addition of the additional constraint to impose the penaltymay also apply to other example embodiments discussed herein.

Additionally, the operating parameter settings are shared with UEs aswell as other base stations, therefore, signaling overhead may beincurred in sharing the selected operating parameter settings with theUEs as well as the other base stations. As an example, in a 3GPP LTEcompliant communications system, the signaling overhead may be realizedin the signaling of user specific reference signals (commonly referredto as demodulation reference signals (DMRS)), which occupy networkresources when signaled. Another constraint may be imposed to reflectthe signaling overhead related to sharing the selected operatingparameter settings with the UEs and the other base stations.

As discussed previously, the selection of the operating parametersettings of the base stations in the cluster may be performed using adistributed technique or a centralized technique. In the distributedtechnique, the base stations may be responsible for performing thecomputations used in the selection of the operating parameter settings.Once the settings of the operating parameters are selected, the basestations share (exchange) the selected operating parameter settings andcontinue until the settings of the operating parameters for the basestations in the cluster are selected. In the centralized technique, thecluster controller or the dedicated entity performs the computationsused in the selection of the operating parameter settings. Once thesettings of the operating parameters of the base stations in the clusterare selected, the operating parameter settings may be distributed to thebase stations in the cluster.

With the operating parameter settings selected, the cluster controllermay share the operating parameter settings for the base stations in thecluster with other clusters (block 415). According to the first exampleembodiment, the operating parameter settings may be shared with all ofthe other clusters in the communications system. Alternatively, theoperating parameter settings may be shared with clusters that are withina specified distance from the cluster, i.e., neighboring clusters.However, the sharing of the operating parameter settings may also applyto other example embodiments discussed herein.

According to the first example embodiment, the operating parametersettings may be used to update the initialized settings of the operatingparameters used by the other clusters when they are selecting operatingparameter settings. However, the updating of the initialized settings ofthe operating parameters to be used by the other clusters may also applyto other example embodiments discussed herein.

The cluster controller may then perform a check to determine whether ornot it will continue selecting the operating parameter settings of thebase stations in the cluster (block 420). With the newly selectedoperating parameter settings received from other clusters, it may bepossible that the initialized settings of the operating parameters forbase stations that are not in the cluster to change. Therefore, theoperating parameter settings of the base station in the cluster may alsochange. Therefore, if there are sufficient computational resources,time, and the like, for example, the cluster controller may re-select atleast some of the operating parameter settings of the base stations inthe cluster. Furthermore, the cluster controller may decide to re-selectat least some of the operating parameter settings of the base stationsin the cluster, but it may decide to delay the re-selection until alater time when more computational resources, time, and the like, areavailable. If the cluster controller re-selects at least some of theoperating parameter settings (i.e., block 410), the cluster controllermay share the re-selected operating parameter settings to the otherclusters (i.e., 415). The cluster controller may also repeat block 420to determine if it will continue selecting the operating parametersettings of the base stations in the cluster. In other words, theselecting of the operating parameter settings and the sharing of theselected operating parameter settings may be repeated a number of times.The cluster controller may send the operating parameter settings to thebase stations in the cluster (block 425).

According to the first example embodiment, once the operating parametersettings have been selected, the cluster controller may further changeserving base station (or similarly, serving cell) assignments of someUEs to help improve the overall performance of the communicationssystem. As an example, a UE that is being served by a macro BS may bereassigned to a pico BS by the cluster controller to help improveoverall communications system performance. The reassignment of UEs frommacro BS to pico BS may help to increase overall gains. However, thechanging of the serving base station may also apply to other exampleembodiments discussed herein.

According to the example embodiment, in addition to reassigning servingbase stations and cells, it may be possible to use multiple pointoperation, such as cooperative multiple point (CoMP) operation withmultiple base stations and/or multiple UEs to transmit to a singlereceiver or multiple receivers to implement a large resource element. Asan example, multiple base stations and/or cells may transmit parts of asingle transmission to a single UE. As another example, multiple UEs mayfeedback information to a single base station or cell. However, the useof CoMP operation may also apply to other example embodiments discussedherein.

As discussed previously, the selection of the operating parametersettings for base stations in clusters may occur in parallel orsequentially. When the selection of the operating parameter settingsoccurs in parallel, the selection of the operating parameter settingsfor the base stations of each cluster may occur at the same time orsubstantially at the same time. As an example, in a communicationssystem with three clusters, the cluster controller for each of the threeclusters may select the operating parameter settings for its basestations simultaneously with the other cluster controllers. While, whenthe selection of the operating parameter settings occurs sequentially,the selection of the operating parameter settings for the base stationsof each cluster may occur one at a time, potentially according to apreferred ordering. With the sequential selection of the operatingparameter settings, the selected operating parameter settings from acluster may be shared with other clusters prior to the clustercontrollers in the other clusters selecting the operating parametersettings for their base stations.

FIG. 4 b illustrates a flow diagram of operations 450 occurring in abase station as it schedules transmissions for its UEs. Operations 450may be indicative of operations occurring in a base station, such asmacro BS 220, macro BS 222, pico BS 224, pico BS 226, macro BS 232, andthe like, of FIG. 2, as the base station schedules transmissions for itsUEs. It is noted that scheduling transmissions includes allocatingnetwork resources to be used in transmitting to the UEs, as well asselecting other parameters, such as data rate, modulating and codingscheme, and the like.

Operations 450 may begin with the base station optionally receiving theoperating parameter settings from a cluster controller (block 455).Operations 450 generally occur after the selection of operatingparameter settings. According to the first example embodiment, if theselection of the operating parameter settings is performed in acentralized manner, as an example, at the cluster controller, adedicated entity, and the like, the base station may receive theoperating parameter settings for itself and other base stations in thecluster from the cluster controller, the dedicated entity, and the like.According to the second example embodiment, if the selection of theoperating parameter settings is performed in a distributed manner, i.e.,the base station participates in the selection of the operatingparameter settings, then the base station already has the operatingparameter settings for itself and other base stations in the cluster anddoes not need to receive the operating parameter settings from thecluster controller, the dedicated entity, and the like.

The base station may estimate a metric for each of its UEs (block 460).According to the first example embodiment, the metric estimated by thebase station may include a signal to interference plus noise ratio(SINR), a signal to noise ratio (SNR), and the like. However, theestimating of the metric may also apply to other example embodimentsdiscussed herein. The base station may estimate the metric using theoperating parameter settings for itself and other base stations in thecluster, the operating parameter settings for base stations not in thecluster, pathloss values for channels between the UEs and other basestations in the cluster, feedback information provided by the UE(including reference signal received power (RSRP) measurements, channelquality indicator (CQI), rank indicator, precoder index, and the like).It is noted that the base station may override some of the feedbackinformation provided by the UE according to channel condition.

As an example, the base station may estimate the pathloss of a channelbetween itself and the UE from the RSRP measurements provided by the UE.Furthermore, the base station may be able to estimate the interferencelevel. The measurements used by the UE for the feedback information aredirected by the base station, so the base station knows which resourcesare used by the UE for measurements. Furthermore, the base station mayalso use CQI feedback from the UEs and transmit power levels from otherbase stations, UE location information, neighbor list information fromthe UEs, uplink pathloss information from other base stations, explicitfeedback from the UEs, or a combination thereof, to help improve metricestimation.

Additionally, the base station (possibly along with other base stationsin the cluster) may estimate a gain to base stations outside of thecluster and adjust the operating parameter settings accordingly. In asituation where the pathloss from the UE to base stations outside of thecluster is not available, the base station may place more weight onlower operating parameter settings to estimate the gain of base stationsoutside of the cluster. Also, the base station may receive informationfrom the base stations outside of the cluster to help in the estimationof gains and/or pathlosses. Additionally, default or expected values forgains and/or pathlosses may be provided to other base stations to allowfor better estimations in the event of lack of actual values.

The base station may schedule UEs for transmission according to theestimated metric (block 465). According to the first example embodiment,the base station selects UEs from its UEs according to the estimatedmetric. As an example, the base station may select UEs with high SINRvalues over UEs with low SINR values. However, the selecting of the UEsaccording to the estimated metric may also apply to other exampleembodiments discussed herein. According to an example embodiment, thebase station may also use other selection criterion to select the UEs.However, the use of other selection criterion may also apply to otherexample embodiments discussed herein. Other selection criterion mayinclude UE priority, available network resources, UE service history,amount of information to transmit to a UE, and the like.

In addition to scheduling UEs, the base station may adjust a data ratefor the scheduled UEs according to the estimated metric. As an example,the base station may reduce the data rate for a first scheduled UE ifits estimated metric (e.g., SINR) is low, while the base station mayincrease the data rate for a second scheduled UE if its estimated metricis high.

According to the first example embodiment, modulation and coding scheme(MCS) adaptation may be utilized to adjust the data rate of thescheduled UEs. There may be several different MCS adaptation processes.However, the MCS adaptation to adjust the date rate of the scheduled UEsmay also apply to other example embodiments discussed herein.

A first MCS adaptation process may involve MCS adaptation during thescheduling of the UEs for calculating an instantaneous data rate of UEsin each RBG. When a UE sends feedback information, e.g., channel stateinformation (CSI) at an n-th transmission time interval (TTI), the basestations determine an interference at the n-th TTI, I_(TTI=n), where theinterference may be determined according to long term pathlossinformation (measured by RSRP in the downlink or sounding referencesignal (SRS) in the uplink, for example). The interference at the n-thTTI is expressible as

${I_{{TTI} = n} = {\sum\limits_{i = 1}^{L}{P_{i,{{TTI} = n}} \times \beta_{i}}}},$

where β_(i) is the pathloss between a UE and neighboring base stationBSi, L is the number of neighboring base stations, and P_(i,TTI=n) isthe operating parameter setting (e.g., transmit power level) of BSi atthe n-th TTI. It is noted that the use of averaging for interference isnot precluded in which P_(i,TTI=n) is replaced by a function of theprevious operating parameters. As an example, the function may be asliding window over the TTI for which the UE is to perform interferencemeasurements.

When determining the instantaneous data rate of the UE at a (n+k)-thTTI, the base station may recalculate the interference at the (n+k)-thTTI, which is expressible as

$I_{{TTI} = {n + k}} = {\sum\limits_{i = 1}^{L}{P_{i,{{TTI} = {n + k}}} \times {\beta_{i}.}}}$

Then, from the feedback information, e.g., CQI, in terms of the MCSlevel, the base station may convert the MCS level into a SINR value atthe n-th TTI, SINR_(TTI=n), to account for short term fading. Anadjusted SINR at the (n+k)-th TTI may then be determined as

${SINR}_{{TTI} = {n + k}} = {{SINR}_{{TTI} = n} \times {\frac{I_{{TTI} = n}}{I_{{TTI} = {n + k}}}.}}$

From the adjusted SINR, the MCS level (and hence the instantaneous datarate) may be chosen for the UE. The adjusted SINR may be improved if thebase station knows the UE's channel matrix rather than the quantized CQIfeedback. With the knowledge of the channel matrix, the base station maybe able to change the transmission rank, the precoder, as well as SINRper layer.

A second MCS adaptation process may involve MCS adaptation after theselection of the operating parameter settings is completed and theoperating parameter settings are shared among the base stations. Thesecond MCS adaptation process may be used to determine a final data rateof the scheduled UEs. The second MCS adaptation process may be performedas follows:

-   -   The interference to each UE may be adjusted based on an updated        operating parameter setting of neighboring base stations;    -   The base stations may determine the utility function results of        each UE and assign RBG(s) to UEs having the largest utility        function result; and    -   If a UE is assigned multiple RBGs, an average SINR may be        calculated across the multiple RBGs. A single MCS level is        chosen for the UE for all of its assigned RBGs. Also, different        MCS levels could be assigned for different RBG.

According to the first example embodiment, the base station may averageUE reported feedback information (e.g., SINR, CQI, and the like) for thepurpose of data rate (MCS) adjustment. However, the averaging of UEreported feedback information may also apply to other exampleembodiments discussed herein. As an example, instead of a most recentlyreported feedback information (e.g., SINR, CQI, and the like), the basestation may average the feedback information reported within a timewindow. Alternatively, the base station may use long term SINR derivedfrom RSRP reports for data rate (MCS) adjustment.

According to the first example embodiment, when the base station has nodata to transmit, e.g., in a subframe, then the base station maytransmit a totally blank data subframe to minimize interference.However, the transmitting of the totally blank data subframe may alsoapply to other example embodiments discussed herein. As an example, in a3GPP LTE compliant communications system, the base station may transmita multicast-broadcast single frequency network (MBSFN) subframe. It isnoted that although the totally blank data subframe may not include anydata (or in some instances, very small amounts of data), the totallyblank data subframe may include control information.

According to the first example embodiment, in a situation wherein thebase station is retransmitting a message due to a transmission failure,the base station may utilize its current operating parameter settings toretransmit the message rather than using the operating parametersettings used to originally transmit the message. However, the use ofcurrent operating parameter settings to retransmit may also apply toother example embodiments discussed herein.

FIG. 5 a illustrates a flow diagram of operations 500 occurring in acluster controller as it participates in a distributed version ofoperating parameter settings selection. Operations 500 may be indicativeof operations occurring in a cluster controller, such as clustercontroller 215 and cluster controller 230, as the cluster controllerparticipates in selecting operating parameter settings for base stationsof a communications system in a distributed fashion.

Operations 500 may begin with the cluster controller selecting aprocessing order for the base stations in the cluster (block 505).According to the second example embodiment, the processing order may beselected by the cluster controller, predetermined by an operator of thecommunications system, specified in a technical standard, and the like.However, the selecting of the processing order may also apply to otherexample embodiments discussed herein. As an example, the processingorder may be made according to factors such as base station type,distance from cluster controller, bandwidth of a connection with thecluster controller, a number of UE supported by the base stations,priority of UE supported by the base stations, and the like.

According to the second example embodiment, the processing order may beused to exclude or include certain types of base stations or specificbase stations. However, the use of the processing order to exclude orinclude certain base stations may also apply to other exampleembodiments discussed herein. As an example, the processing order may beused to exclude pico base stations from the selection of operatingparameter settings by simply not listing the pico base stations in theprocessing order. Similarly, specific base stations may be excluded bysimply not listing the specific base stations in the processing order.Although the pico base stations are considered to be part of a clusterand they may be considered in the selection of operating parametersettings for macro base station, pico base stations are generally lowpower devices and it may be desirable to not select operating parametersettings for pico base stations to reduce computational complexity inthe selecting of operating parameter settings for other base stations,such as macro base stations.

The cluster controller may initiate an optimization of the operatingparameter settings of the base stations in the cluster according to theselected processing order (block 510). As an example, if the selectedprocessing order may be base station 1, base station 3, base station 4,and base station 2 for a cluster with four base stations, then thecluster controller may initiate the selection of the operating parametersettings so that the operating parameter settings of base station 1 areselected first, followed by the selection of the operating parametersettings for base station 3, base station 4, and then base station 2.The cluster controller may share (exchange) the operating parametersettings with other clusters (block 515). According to the secondexample embodiment, the operating parameter settings may be shared withall of the other clusters in the communications system. However, thesharing of the operating parameter settings may also apply to otherexample embodiments discussed herein. Alternatively, the operatingparameter settings may be shared with clusters that are within aspecified distance from the cluster, i.e., neighboring clusters.

Generally, the operating parameter settings of a base station in acluster may differ for different TTIs. Therefore, the selection of theoperating parameter settings may be performed for each TTI. However, theselection of the operating parameter settings for each TTI may require asignificant amount of computational resources, which may not beavailable or may be used elsewhere.

According to the second example embodiment, semi-static operationalparameter setting selection may be used to reduce the number of timesthat the selection of the operating parameter settings is performed,thereby reducing computational requirements. However, the semi-staticoperating parameter setting selection may also apply to other exampleembodiments discussed herein. As an example, the operating parametersettings from a previous TTI may be used for a current TTI rather thanselecting new operating parameter settings. Additionally, historicalinformation may be used to select which operating parameter settings tobe used for the TTI. As an example, historical information may be usedto select operational parameter settings most often used incorresponding TTIs.

According to the second example embodiment, sample and hold operatingparameter settings may be used to reduce the number of times that theselection of the operating parameter settings is performed, therebyreducing computational requirements. However, the sample and holdoperating parameter settings may also apply to other example embodimentsdiscussed herein. As an example, the operating parameter settings may beselected for a TTI and then used for a plurality of subsequent TTIs. Anumber of TTIs in the plurality of subsequent TTIs may be apre-configured value, may be dependent on operating conditions of thecommunications system, UE mobility, and the like.

According to an example embodiment, delayed operating parameter settingsmay be used to reduce the number of times that the selection of theoperating parameter settings is performed, thereby reducingcomputational requirements, as well as allowing for communication and/orprocessing delays in selecting the operating parameter settings.However, the delayed operating parameter settings may also apply toother example embodiments discussed herein. As an example, the operatingparameter settings may be selected for a k-th TTI, but not applied untila (k+C)-th TTI, where C is a constant representing UE schedulingperiodicity. By selecting the operating parameter settings before theyare actually needed, computational restraints according to real-timerequirements may be relaxed.

FIG. 5 b illustrates a flow diagram of operations 550 occurring in abase station as it participates in a distributed version of operatingparameter setting selection, wherein the base station is selecting itsoperating parameter settings. Operations 550 may be indicative ofoperations occurring in a base station, such as macro BS 220, macro BS222, pico BS 224, pico BS 226, macro BS 232, and the like, of FIG. 2, asthe base station participates in selecting operating parameter settingsfor base stations of a communications system in a distributed fashion.

Operations 550 may begin with the base station initializing itsoperating parameter settings (block 555). According to the secondexample embodiment, initializing the operating parameter settings mayinclude the base station determining possible settings for the operatingparameters. However, the base station determining possible settings mayalso apply to other example embodiments discussed herein. As an example,if the operating parameter is a transmit power level, then initializingthe operating parameter setting includes determining a set of possibletransmit power levels for the base station. While, if the operatingparameter is a precoder, then initializing the operating parametersetting includes determining a set of possible precoders that the basestation may use, or conversely a set of null precoders which the basestation may not use (i.e., an indication of where interference will notbe generated)

The base station may share (exchange) the operating parameter settings,i.e., the possible settings of the operating parameters, to other basestations in the cluster (block 557). The base station may receiveutility function results from the other base stations in the cluster(block 559). According to the second example embodiment, the other basestations in the cluster determine their utility function resultsaccording to the operating parameter settings shared by the basestation, as well as initialized settings of the operating parameter frombase stations not in the cluster. However, the base stations determiningtheir utility function results according to the operating parametersettings as well as initialized settings of base stations not in thecluster may also apply to other example embodiments discussed herein.

As an example, considering a situation with a cluster having two basestations (a first base station (BS1) and a second base station (BS2))with two other clusters in the communications system, with the firstbase station selecting its operating parameter settings. Furthermore, ifthe operating parameter is a transmit power level and for the first basestation in the cluster, there are two possible settings for the transmitpower level (TPL1_1, and TPL1_2) and for the second base station in thecluster, there are three possible settings for the transmit power level(TPL2_1, TPL2_2, and TPL_2_3). Then, the first base station shares itstransmit power levels (TPL1_1, and TPL1_2) with the second base stationand receives utility function results from the second base station. Asan example, the second base station may determine its utility functionresults as follows:

Utility(BS2, TPL1_1) = Utility_Function_BS2(TPL1_1, initialized_BS2,initialized_outsidecluster_1, initialized_outsidecluster_2); andUtility(BS2, TPL1_2) = Utility_Function_BS2(TPL1_2, initialized_BS2,initialized_outsidecluster_1, initialized_outsidecluster_2),where Utility(BS2,X) represents the utility function result from thesecond base station for operating parameter setting X, initialized_BS2is an initialized setting of the operating parameter for the second basestation, initialized_outsidecluster_1 is an initialized setting of theoperating parameter for a first other cluster, andinitialized_outsidecluster_2 is an initialized setting of the operatingparameter for a second other cluster.

The base station may determine its own utility function result for itspossible operating parameter settings (block 561). According to thesecond example embodiment, the base station determines its own utilityfunction results for its possible operating parameter settings andinitialized settings (or previously selected operating parametersettings) of other base stations in the cluster and initialized settings(or previously selected operating parameter settings) of base stationsin other clusters. However, the base station determining its own utilityfunction results for its possible operating parameter settings andinitialized settings of other base stations also apply to other exampleembodiments discussed herein.

As an example, revisiting the above situation with the cluster havingtwo base stations, and neither base station having selected itsoperating parameters. Then the first base station may determine itsutility function results as:

Utility(BS1, TPL1_1) = Utility_Function_BS1(TPL1_1, initialized_BS2,initialized_outsidecluster_1, initialized_outsidecluster_2); andUtility(BS1, TPL1_2) = Utility_Function_BS1(TPL1_2, initialized_BS2,initialized_outsidecluster_1, initialized_outsidecluster_2).

As another example, considering a situation wherein the first basestation has already determined its operating parameter settings, and thesecond base station is selecting its operating parameter settings, thenthe first base station may provide to the second base station itsutility function results expressible as (with an assumption that thefirst base station has selected TPL1_2 as its operating parameter, forexample)

Utility(BS1, TPL2_1) = Utility_Function_BS1(TPL1_2, TPL2_1,initialized_outsidecluster_1, initialized_outsidecluster_2);Utility(BS1, TPL2_2) = Utility_Function_BS1(TPL1_2, TPL2_2,initialized_outsidecluster_1, initialized_outsidecluster_2); andUtility(BS1, TPL2_3) = Utility_Function_BS1(TPL1_2, TPL2_3,initialized_outsidecluster_1, initialized_outsidecluster_2).The second base station may determine its own utility function resultsas follows

Utility(BS2,TPL2_1) = Utility_Function_BS2(TPL1_2, TPL2_1,initialized_outsidecluster_1, initialized_outsidecluster_2);Utility(BS2,TPL2_2) = Utility_Function_BS2(TPL1_2, TPL2_2,initialized_outsidecluster_1, initialized_outsidecluster_2); andUtility(BS2,TPL2_3) = Utility_Function_BS2(TPL1_2, TPL2_3,initialized_outsidecluster_1, initialized_outsidecluster_2).

With its utility function results determined and having received utilityfunction results from other base stations in the cluster, the basestation may optimally select its operating parameter settings (block563). According to an example embodiment, the base station may sum uputility function results associated with each possible operatingparameter setting and select an operating parameter setting that resultsin the largest summed value. According to an alternative exampleembodiment, the base station may sum up utility function resultsassociated with each possible operating parameter setting and select anoperating parameter setting that results in the smallest summed value.

As an example, revisiting the above situation with the cluster havingtwo base stations, the first base station may perform two summations(one for each of its two possible operating parameter settings):

Summation(TPL1_1) = Utility(BS2, TPL1_1) + Utility(BS1, TPL1_1); andSummation(TPL1_2) = Utility(BS2, TPL1_2) + Utility(BS1, TPL1_2),where Summation(X) is the summation for operating parameter setting X.

As another example, revisiting the above situation, but with the firstbase station having already determined its operating parameters, thesecond base station may perform three summations (one for each of itsthree possible operating parameter settings):

Summation(TPL2_1) = Utility(BS1, TPL2_1) + Utility(BS2, TPL2_1);Summation(TPL2_2) = Utility(BS1, TPL2_2) + Utility(BS2, TPL2_2); andSummation(TPL2_3) = Utility(BS1, TPL2_3) + Utility(BS2, TPL2_3).

In the description of block 563 presented above, the base stationconsiders its own utility function results along with utility functionresults from other base stations in the cluster in the selection of theoperating parameter settings. However, it is also possible for the basestation to also consider utility function results from base stationsoutside of the cluster in the selection of the operating parametersettings.

Generally, when selecting operating parameter settings for base stationsof clusters in parallel, it may be difficult to calculate an impact ofan operating parameter setting of a base station inside the cluster onutility function results of base stations outside of the cluster.However, it may be possible to estimate the impact on the utilityfunction results of base stations outside of the cluster. The estimatedimpact on the utility function results of base stations outside of thecluster may then be considered when selecting the operating parametersettings of base stations inside the cluster.

As an example, consider a base station denoted BS_(k), then the utilityfunction for the communications system, given that the operatingparameter setting of BS_(k) is denoted P_(j) (e.g., transmit powerlevel), may be expressible as

$\begin{matrix}{{U\left( {\left. {{whole}\mspace{14mu} {system}} \middle| {P\left( {BS}_{k} \right)} \right. = P_{j}} \right)} = {{U_{i\; n}\left( {{P\left( {BS}_{k} \right)} = P_{j}} \right)} +}} \\{{U_{out}\left( {{P\left( {BS}_{k} \right)} = P_{j}} \right)}} \\{= {W\left( {{BS}_{k},P_{j}} \right) \times}} \\{{{U_{i\; n}\left( {{P\left( {BS}_{k} \right)} = P_{j}} \right)},}}\end{matrix}$ where${{U_{i\; n}\left( {{P\left( {BS}_{k} \right)} = P_{j}} \right)} = {\sum\limits_{i = 1}^{\# \mspace{14mu} {of}\mspace{14mu} {BS}\mspace{14mu} {of}\mspace{14mu} {cluster}}{U\left( {\left. {BS}_{i,{i\; n}} \middle| {P\left( {BS}_{k} \right)} \right. = P_{j}} \right)}}},{{U_{out}\left( {{P\left( {BS}_{k} \right)} = P_{j}} \right)} = {\sum\limits_{i = 1}^{\# \mspace{14mu} {of}\mspace{14mu} {BS}\mspace{14mu} {outside}\mspace{14mu} {of}\mspace{14mu} {cluster}}{{U\left( {\left. {BS}_{i,{out}} \middle| {P\left( {BS}_{k} \right)} \right. = P_{j}} \right)}.}}}$

and a utility function weight W(BS_(k), P_(j)) may be expressible as

${W\left( {{BS}_{k},P_{j}} \right)} = {\frac{{U_{i\; n}\left( {{P\left( {BS}_{k} \right)} = P_{j}} \right)} + {U_{out}\left( {{P\left( {BS}_{k} \right)} = P_{j}} \right)}}{U_{i\; n}\left( {{P\left( {BS}_{k} \right)} = P_{j}} \right)}.}$

It is noted that U_(in) (P(BS_(k))=P_(j)) includes the utility functionof BS_(k).

In practice, when the selection of the operating parameter settings isperformed in parallel, it may be difficult to determine the utilityfunction results for base stations outside of the cluster. However, itmay be possible to approximate the utility function weight W(BS_(k),P_(j)) from long term utility function results. As an example,considering a situation wherein information is transmitted from a basestation BS, to a neighboring base station BS_(k). For each RBG, theinformation may include: utility function results for scheduled UE(s);and a neighbor list of the scheduled UE(s). The neighbor list mayprovide information about which neighboring base station needs to updatetheir utility function weights. Table 1 illustrates example neighborlists for base station BS_(i).

TABLE 1 Example Neighbor Lists. Utility RBG-1 Utility RBG-2 UtilityRBG-3 Neighbor list RBG-1 Neighbor list RBG-2 Neighbor list RBG-3 BS2,BS3, BS4 BS3 BS3, BS4

As shown in Table 1, base station BS2 only needs to update its utilityfunction weight in RBG-1, while base station BS4 needs to update itsutility function weight in RBG-1 and RBG-3, and base station BS3 needsto update its utility function weight in RBG-1, RBG-2, and RBG-3.

According to the second example embodiment, the utility function weightW(BS_(k), P_(j)) is calculated using a long term average of utilityfunction results of base stations in the cluster and base stationsoutside the cluster, however, other mathematical functions may be used.However, the calculating of the utility function weight using the longterm average may also apply to other example embodiments discussedherein. As an example, at every TTI (or at specified TTIs), the utilityfunction results of base stations in the cluster and base stationsoutside the cluster may be updated whenever a corresponding base stationis included in neighbor list information provided by an impacted basestation. The updating of the utility function results may be expressedas

${U_{{i\; n},{{TTI} = n}}\left( {{P\left( {BS}_{k} \right)} = P_{j}} \right)} = {{\gamma_{{BS}_{k,{i\; n}}}{U_{{i\; n},{{TTI} = {n - 1}}}\left( {{P\left( {BS}_{k} \right)} = P_{j}} \right)}} + {\sum\limits_{i = 1}^{\# \mspace{14mu} {of}\mspace{14mu} {Neighbors}}{U\left( {{\left. {BS}_{i,{i\; n}} \middle| {P\left( {BS}_{k} \right)} \right. = P_{j}},{k \in {{Neighbor}\mspace{14mu} {list}\mspace{14mu} {of}\mspace{14mu} {BS}_{i}}}} \right)}}}$and${{U_{{out},{{TTI} = n}}\left( {{P\left( {BS}_{k} \right)} = P_{j}} \right)} = {{\gamma_{{BS}_{k,{out}}}{U_{{out},{{TTI} = {n - 1}}}\left( {{P\left( {BS}_{k} \right)} = P_{j}} \right)}} + {\sum\limits_{i = 1}^{\# \mspace{14mu} {of}\mspace{14mu} {Neighbors}}{U\left( {{\left. {BS}_{i,{out}} \middle| {P\left( {BS}_{k} \right)} \right. = P_{j}},{k \in {{Neighbor}\mspace{14mu} {list}\mspace{14mu} {of}\mspace{14mu} {BS}_{i}}}} \right)}}}},$

where γ_(BS) _(k,in) and γ_(BS) _(k,out) are constants used indetermining the weighting of an accumulated utility of the historicutility function results in newly accumulated utility function weightsfor base stations inside the cluster and base stations outside thecluster, respectively.

Additionally, applying utility weights for the selected operatingparameter settings may be difficult if pathloss information from UEs tosome base stations is not available. It might not be possible toestimate the interference from those base stations if their operatingparameter settings have changed. It may be possible to apply differentweights on the sum utility. More weight may be added to some settings toestimate the performance gain and/or loss of some base stations whosepathloss to the UE is unknown. It may also be possible to exchangethroughput gain and/or loss among the base stations when a base stationuses specific operating parameter settings, the surrounding basestations may estimate the performance difference compared to a situationwhen the base station uses default or initialized operating parametersettings. The estimated gain and/or loss may be used to determine theutility weights.

The base station may share the selected operating parameter settingswith other base stations in the cluster (block 565). The base stationmay also report the selected operating parameter settings to the clustercontroller (block 567).

FIG. 5 c illustrates a flow diagram of operations 575 occurring in abase station as it participates in a distributed version of operatingparameter setting selection, wherein the base station is assistinganother base station select its operating parameter settings. Operations575 may be indicative of operations occurring in a base station, such asmacro BS 220, macro BS 222, pico BS 224, pico BS 226, macro BS 232, andthe like, of FIG. 2, as the base station participates in selectingoperating parameter settings for base stations of a communicationssystem in a distributed fashion.

Operations 575 may begin with the base station receiving operatingparameter settings from one or more base stations that have selectedtheir operating parameter settings (block 580). As discussed previously,the base stations may select their operating parameter settingsaccording to a selected processing order and a base station usesselected operating parameter settings when assisting other base stationsin its selection of operating parameter settings. If there are one ormore base stations in the cluster that have not selected their operatingparameter settings, then initialized operating parameter settingsassociated with these base stations may be used.

The base station may receive possible operating parameter settings fromthe base station that is selecting its operating parameter settings(block 582). The base station may then determines its utility functionresults according to the possible operating parameter settings, selectedoperating parameter settings for base stations that have selected theiroperating parameter settings, initialized operating parameter settingsfor base stations in the cluster that have not selected their operatingparameter settings, initialized settings for base stations not in thecluster, or combinations thereof.

As an example, considering a situation with a cluster having two basestations (a first base station (BS1) and a second base station (BS2))with two other clusters in the communications system, with the secondbase station assisting the first base station in selecting its operatingparameter settings. Furthermore, the operating parameter is a transmitpower level and for the first base station in the cluster, there are twopossible settings for the transmit power level (TPL1_1, and TPL1_2) andfor the second base station in the cluster, there are three possiblesettings for the transmit power level (TPL2_1, TPL2_2, and TPL2_3). Thesecond base station may determine its utility function results asfollows

Utility(BS2, TPL1_1) = Utility_Function_BS2(TPL1_1, initialized_BS2,initialized_outsidecluster_1, initialized_outsidecluster_2); andUtility(BS2, TPL1_2) = Utility_Function_BS2(TPL1_2, initialized_BS2,initialized_outsidecluster_1, initialized_outsidecluster_2).

The base station may share its utility function results with the basestation that is selecting its operating parameter settings (block 586)and then receive, from the base station that is selecting its operatingparameter settings, the selected operating parameter settings (block588).

FIG. 6 illustrates a flow diagram of operations 600 occurring in acluster controller as it participates in a centralized version ofoperating parameter selection. Operations 600 may be indicative ofoperations occurring in a cluster controller, such as cluster controller215 and cluster controller 230, as the cluster controller participatesin selecting operating parameter settings for base stations of acommunications system in a centralized fashion.

Operations 600 may begin with the cluster controller initializingoperating parameter settings of base stations in its cluster (block605). The cluster controller may also select a processing order for thebase stations in its cluster (block 610).

The cluster controller may select a base station for operating parametersetting selection according to the selected processing order (block615). For the selected base station, the cluster controller maydetermine utility function results for the selected base station as wellas for other base stations in the cluster for the selected basestation's operating parameter settings (block 620). According to thefirst example embodiment, for base stations that are in and out of thecluster that do not have selected operating parameter settings, thecluster controller may use initialized operating parameter settings.However, the use of initialized operating parameter settings for basestations that do not have selected operating parameter settings may alsoapply to other example embodiments discussed herein. To optimize theoperating parameter settings, the cluster controller may select anoperating parameter setting that maximizes (or minimizes), for example,summations of utility function results of the base stations in thecluster (block 625).

The cluster controller may then perform a check to determine if thereare any additional base stations with operating parameter settings toselect (block 630). If there are additional base stations, then thecluster controller may return to block 615 to repeat the operatingparameter setting selection process with another base station. If thereare no more base stations, then the cluster controller may store theselected operating parameter settings for subsequent use (block 635).

In a heterogeneous communications system with base stations of differentcapabilities, e.g., macro BS and pico BS, the macro BS may selectsettings for some operating parameters such as transmit power level,which may be lower than a nominal value to help UEs served by pico BS.To increase the gain of a UE served by a pico BS, it may be possible toincrease the number of UEs served by the pico BS by applying a cellselection bias when searching for a serving base station or transmittingdata using a pico BS while the UE receives control signaling from amacro BS.

Additionally, under certain circumstances, the transmit power level forsome base stations may be zero. This may imply that interference fromthese base stations to UEs of other base stations is too great. In sucha situation, the control signals and the pilot signals from these basestations may be switched off. As an example, the switching off of thecontrol signals and the pilot signals may be achieved using MBSFNsubframes in a 3GPP LTE compliant communications system.

FIG. 7 a illustrates a diagram of a first communications device 700.Communications device 700 may be an implementation of a clustercontroller of a cluster of a communications system or a dedicated entityin the communications system that selects operating parameter settings.Communications device 700 may be used to implement various ones of theembodiments discussed herein. As shown in FIG. 7 a, a transmitter 705 isconfigured to send messages, operating parameter settings, utilityfunction results, base station processing order information, and thelike, and a receiver 710 is configured to receive messages, operatingparameter settings, utility function results, and the like. Transmitter705 and receiver 710 may have a wireless interface, a wirelineinterface, or a combination thereof.

A parameter initializing unit 720 is configured to initialize operatingparameters for base stations in a cluster controlled by communicationsdevice 700. Parameter initializing unit 720 may initialize the operatingparameter settings to default or pre-specified settings or to previouslyselected settings. A parameter selecting unit 722 is configured toselect operating parameter settings for base stations in the clustercontrolled by communications device 700. Parameter selecting unit 722may operate in a distributed manner or a centralized manner. Detaileddescriptions of parameter selecting unit 722 for distributed operationand centralized operation is provided below. A parameter sharing unit724 is configured to share the operating parameter settings with otherbase station in the cluster as well as base stations outside of thecluster. A memory 730 is configured to store initialized operatingparameter settings, selected operating parameter settings, processingorder information, utility function results, and the like.

The elements of communications device 700 may be implemented as specifichardware logic blocks. In an alternative, the elements of communicationsdevice 700 may be implemented as software executing in a processor,controller, application specific integrated circuit, or so on. In yetanother alternative, the elements of communications device 700 may beimplemented as a combination of software and/or hardware.

As an example, transmitter 705 and receiver 710 may be implemented as aspecific hardware block, while parameter initializing unit 720,parameter selecting unit 722, and parameter sharing unit 724 may besoftware modules executing in a processor 715, such as a microprocessor,a digital signal processor, a custom circuit, or a custom compiled logicarray of a field programmable logic array.

FIG. 7 b illustrates a detailed view of parameter selecting unit 750that operates in a distributed manner. In general, when operating in thedistributed manner, parameter selecting unit 750 off-loads operations toselect the operating parameter settings to base stations in the cluster.A processing order selecting unit 752 is configured to select anoperating parameter setting selecting order for base stations in thecluster. As an example, the selected processing order may be madeaccording to factors such as base station type, distance from clustercontroller, bandwidth of a connection with the cluster controller, anumber of UE supported by the base stations, priority of UE supported bythe base stations, and the like. An initiating unit 754 is configured toinitiate operations at base stations in the cluster according to theoperating parameter setting selecting order to select operatingparameter settings for the base stations in the cluster.

FIG. 7 c illustrates a detailed view of parameter selecting unit 770that operates in a centralized manner. In general, when operating in thecentralized manner, parameter selecting unit 770 performs the operationsto select the operating parameter settings of base stations in thecluster. A processing order selecting unit 772 is configured to selectan operating parameter setting selecting order for base stations in thecluster. As an example, the selected processing order may be madeaccording to factors such as base station type, distance from clustercontroller, bandwidth of a connection with the cluster controller, anumber of UE supported by the base stations, priority of UE supported bythe base stations, and the like.

A base station selecting unit 774 is configured to select a base stationaccording to the operating parameter setting selecting order that hasnot had its operating parameter settings selected. A utility functiondetermining unit 776 is configured to determine utility function resultsaccording to possible operating parameter settings, initializedoperating parameter settings, selected operating parameter settings,initialized settings for base stations not in the cluster, or acombination thereof. A parameter selecting unit 778 is configured todetermine summations of utility function results associated with variouspotential operating parameter settings to optimize the operatingparameter setting selection, by selecting an operating parameter settingthat maximizes (or minimizes), for example, the summation.

FIG. 8 illustrates a diagram of a second communications device 800.Communications device 800 may be an implementation of a base station ofa cluster of a communications system. Communications device 800 may beused to implement various ones of the embodiments discussed herein. Asshown in FIG. 8, a transmitter 805 is configured to send messages,operating parameter settings, utility function results, and the like,and a receiver 810 is configured to receive messages, operatingparameter settings, utility function results, and the like. Transmitter805 and receiver 810 may have a wireless interface, a wirelineinterface, or a combination thereof.

An estimating unit 820 is configured to estimate a metric (such as, aSINR, a SNR, and the like) for UEs served by communications device 800.A scheduling unit 822 is configured to schedule UEs for transmissionaccording to the estimated metric. According to an example embodiment,scheduling unit 822 selects UEs from its UEs according to the estimatedmetric. As an example, scheduling unit 822 may select UEs with high SINRvalues over UEs with low SINR values. According to an exampleembodiment, scheduling unit 822 may also use other selection criterionto select the UEs. Other selection criterion may include UE priority,available network resources, UE service history, amount of informationto transmit to a UE, and the like. An adjusting unit 824 is configuredto adjust a data rate for the scheduled UEs according to the estimatedmetric. As an example, the base station may reduce the data rate for afirst scheduled UE if its estimated metric (e.g., SINR) is low, whilethe base station may increase the data rate for a second scheduled UE ifits estimated metric is high.

A utility function determining unit 826 is configured to determineutility function results according to possible operating parametersettings, initialized operating parameter settings, selected operatingparameter settings, initialized settings for base stations in thecluster, initialized settings for base stations not in the cluster, or acombination thereof. A parameter selecting unit 828 is configured todetermine summations of utility function results associated with variouspotential operating parameter settings to optimize the operatingparameter settings, by selecting an operating parameter setting thatmaximizes (or minimizes), for example, the summation. An operatingparameter sharing unit 830 is configured to share the operatingparameter settings with other base stations, as well as a clustercontroller. A memory 840 is configured to store initialized operatingparameter settings, selected operating parameter settings, processingorder information, utility function results, and the like.

The elements of communications device 800 may be implemented as specifichardware logic blocks. In an alternative, the elements of communicationsdevice 800 may be implemented as software executing in a processor,controller, application specific integrated circuit, or so on. In yetanother alternative, the elements of communications device 800 may beimplemented as a combination of software and/or hardware.

As an example, transmitter 805 and receiver 810 may be implemented as aspecific hardware block, while estimating unit 820, scheduling unit 822,adjusting unit 824, utility function determining unit 826, parameterselecting unit 828, and parameter sharing unit 830 may be softwaremodules executing in a processor 815, such as a microprocessor, adigital signal processor, a custom circuit, or a custom compiled logicarray of a field programmable logic array.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the invention as defined by the appended claims.

1. A method for configuring a first base station within a cluster in acommunications system having a plurality of cluster, the methodcomprising: optimizing, by a processor in the first base station, anoperating parameter of the first base station in accordance with firstutility function results from a first utility function associated withthe first base station and second utility function results from a secondutility function associated with a second base station within thecluster, the first utility function results and the second utilityfunction results generated in accordance with multiple settings for theoperating parameter of the first base station, a first initializedsetting of the operating parameter for the second base station, and asecond initialized setting of the operating parameter for an externalbase station outside the cluster; and sharing the optimized operatingparameter with the external base station.
 2. The method of claim 1,wherein each of the first utility function results and the secondutility function results is associated with one of the multiple settingsfor the operating parameter, and wherein optimizing the operatingparameter comprises: determining, for each of the multiple settings ofthe operating parameter, a summation of the first utility functionresults and the second utility function results; and selecting one ofthe multiple settings in accordance with a comparison of the summationfor each of the multiple settings of the operating parameter as theoptimized operating parameter for the first base station.
 3. The methodof claim 2, wherein selecting one of the multiple settings comprisesselecting one of the multiple settings with a maximum summation.
 4. Themethod of claim 2, wherein selecting one of the multiple settingscomprises selecting one of the multiple settings with a minimumsummation.
 5. The method of claim 1, wherein the operating parametercomprises a transmit power level, a precoder index, a modulation andcoding scheme of a transmission, a location of a reference signal, apilot signal boosting level, frequency selective scheduling or frequencydiversity scheduling, a handover parameter, antenna tilt, antennapattern, transmission rank, or a combination thereof.
 6. The method ofclaim 1, wherein the first utility function comprises one of aninstantaneous data rate for a user equipment served by the first basestation and a calculated function of the instantaneous data rate for theuser equipment served by the first base station.
 7. The method of claim1, further comprising optimizing the operating parameter of the secondbase station in accordance with updated first utility function resultsfrom the first utility function associated with the first base stationand updated second utility function results from the second utilityfunction associated with the second base station, the updated firstutility function results and the updated second utility function resultsgenerated in accordance with the optimized operating parameter of thefirst base station, multiple settings for the operating parameter of thesecond base station, and the second initialized setting of the operatingparameter for the external base station outside the cluster.
 8. Themethod of claim 1, further comprising: receiving an optimized externalparameter from the external base station; updating the secondinitialized setting of the operating parameter for the external basestation with the optimized external parameter; and repeating optimizingthe operating parameter. 9-22. (canceled)
 23. A first base stationcomprising: a processor configured to optimize an operating parameter ofthe first base station in accordance with first utility function resultsfrom a first utility function associated with the first base station andsecond utility function results from a second utility functionassociated with a second base station within a cluster, the firstutility function results and the second utility function resultsgenerated in accordance with multiple settings for the operatingparameter of the first base station, a first initialized setting of theoperating parameter for the second base station, and a secondinitialized setting of the operating parameter for an external basestation outside the cluster; and a transmitter operatively coupled tothe processor, the transmitter configured to transmit the optimizedoperating parameter with the external base station.
 24. The base stationof claim 23, wherein the processor is configured to determine, for eachof the multiple settings of the operating parameter, a summation of thefirst utility function results and the second utility function results,and to select one of the multiple settings in accordance with acomparison of the summation for each of the multiple settings of theoperating parameter as the optimized operating parameter for the firstbase station.
 25. The base station of claim 23, wherein the processor isconfigured to optimize the operating parameter of the second basestation in accordance with updated first utility function results fromthe first utility function associated with the first base station andupdated second utility function results from the second utility functionassociated with the second base station, the updated first utilityfunction results and the updated second utility function resultsgenerated in accordance with the optimized operating parameter of thefirst base station, multiple settings for the operating parameter of thesecond base station, and the second initialized setting of the operatingparameter for the external base station outside the cluster.
 26. Thebase station of claim 23, further comprising a receiver operativelycoupled to the processor, the receiver configured to receive anoptimized external parameter from the external base station, and whereinthe processor is configured to update the second initialized setting ofthe operating parameter for the external base station with the optimizedexternal parameter.
 27. The base station of claim 24, wherein theprocessor configured to select one of the multiple settings comprisesthe processor configured to select one of the multiple settings with amaximum summation.
 28. The base station of claim 24, wherein theprocessor configured to select one of the multiple settings comprisesthe processor configured to select one of the multiple settings with aminimum summation.
 29. The base station of claim 23, wherein theoperating parameter comprises a transmit power level, a precoder index,a modulation and coding scheme of a transmission, a location of areference signal, a pilot signal boosting level, frequency selectivescheduling or frequency diversity scheduling, a handover parameter,antenna tilt, antenna pattern, transmission rank, or a combinationthereof.
 30. The base station of claim 23, wherein the first utilityfunction comprises one of an instantaneous data rate for a userequipment served by the first base station and a calculated function ofthe instantaneous data rate for the user equipment served by the firstbase station.
 31. The base station of claim 30, wherein the calculatedfunction is ${\log\left( \frac{r_{i}}{r_{avg}} \right)},$ where r_(i) isan instantaneous data rate of an i-th user equipment, and r_(avg) is anaverage data rate of the i-th user equipment.
 32. The method of claim 6,wherein the calculated function is${\log\left( \frac{r_{i}}{r_{avg}} \right)},$ where r_(i) is aninstantaneous data rate of an i-th user equipment, and r_(avg) is anaverage data rate of the i-th user equipment.